docs: move first paragraph close to footnote return link

Footnotes used to look like:

  [1]

  first paragraph starts 1.2 em away because of default * + * spacing.
  More paragraph lines. ...

It looks wrong. The return link should be closer to the first
paragraph so they are seen as more of a unit. Ideally the return link
'[1]' should be a hanging indent and all paragraphs for the footnote
should be indented. But I can't figure out how to do that. So tighten
up the space before the first paragraph.

  [1]
  So the first paragraph after the label starts right below it tying
  the footnote to the text.

Author: rouilj

doc/_static/style.css

@@ -489,6 +489,8 @@ table.valign-top tbody td { vertical-align: top; }
   padding-inline: 1em;
 }
 
+aside.footnote > span + p { margin-block-start: unset; }
+
 /* consider highlighting header element that is a target */
 /*
 :target > :is(h1,h2,h3,h4,h5,h6) {

website/www/_static/style.css

@@ -489,6 +489,8 @@ table.valign-top tbody td { vertical-align: top; }
   padding-inline: 1em;
 }
 
+aside.footnote > span + p { margin-block-start: unset; }
+
 /* consider highlighting header element that is a target */
 /*
 :target > :is(h1,h2,h3,h4,h5,h6) {